Method and arrangement for transferring information in a packet radio service

ABSTRACT

The invention relates generally to a method and an arrangement for transferring information in a packet radio service. Especially the invention applies to transferring delay sensitive data, such as speech and video data, in a mobile telecommunications system. It is an object of this invention to provide a solution, in which the physical connection of a packet radio service is kept reserved also during the passive periods of a session but the same physical resource can still be shared between multiple users. A basic idea of the invention is that the network is informed at the end of an active period, on whether a passive period follows the active period or if the connection can be released. When an active period starts after a passive period, the connection preferably reserves the packet data channel again, and possible other users of the channel are assigned to other channels.

[0001] The invention relates generally to a method and an arrangementfor transferring information in a packet radio service. Especially theinvention applies to transferring delay sensitive data, such as speechand video data, in a mobile telecommunications system.

[0002] The denomination “mobile telecommunications system” refersgenerally to any telecommunications system which enables a wirelesscommunication connection between a mobile station (MS) and the fixedparts of the system when the user of the mobile station is moving withinthe service area of the system. A typical mobile communications systemis a Public Land Mobile Network (PLMN). The majority of mobiletelecommunications systems in use at the time of the filing of thispatent application belong to the second generation of such systems, awell-known example being the GSM system (Global System for Mobiletelecommunications). However, the invention also applies to the next orthird generation of mobile telecommunications systems, such as a systemknown as the UMTS (Universal Mobile Telecommunications System) whichcurrently undergoes standardisation.

[0003] Internet real time services have gained popularity during thepast few years. IP (Internet Protocol) telephony and different streamingapplications are already common in the Internet. Also the demand forwireless access to these real time services is expected to be stillgrowing. Packet switched wireless networks, such as GPRS (General PacketRadio Service), are designed to provide data services, e.g. Internetservices, cost effectively. In GPRS the channels are not dedicated forone user continuously but are shared between multiple users. Thisfacilitates efficient data multiplexing. However, GPRS is not originallydesigned for transferring delay sensitive real time data, e.g. IPtelephony sessions. For this reason, GPRS contains various technicalsolutions that do not meet the requirements set by real time traffic. Inthe following text, a denomination “delay sensitive data” is used fordata flows that should be transferred on real time basis and that mayhave passive periods during which the data flow is suspended.

[0004] In order to better understand the problems of the prior artsolutions and the idea of the present invention, the structure of athird generation digital cellular radio system is first shortlydescribed, and GPRS is then described in more detail.

[0005]FIG. 1a shows a version of a future cellular radio system which isnot entirely new compared to the known GSM system but which includesboth known elements and completely new elements. The terminals areconnected to the radio access network RAN which includes the basestations and the base station controllers. The core network of acellular radio system comprises mobile services switching centres (MSC),other network elements (in GSM, e.g. SGSN and GGSN, i.e. Serving GPRSSupport Node and Gateway GPRS Support node, where GPRS stands forGeneral Packet Radio Service) and related transmission systems.According, e.g. to the GSM+ specifications developed from GSM, the corenetwork can also provide new services.

[0006] In FIG. 1a, the core network of a cellular radio system 10comprises a GSM+ core network 11 which has three parallel radio accessnetworks linked to it. Of those, networks 12 and 13 are UMTS radioaccess networks and network 14 is a GSM+ radio access network. The upperUMTS radio access network 12 is, e.g. a commercial radio access network,owned by a telecommunications operator offering mobile services, whichequally serves all subscribers of said telecommunications operator. Thelower UMTS radio access network 13 is, e.g. private and owned e.g. by acompany in whose premises said radio access network operates. Typicallythe cells of the private radio access network 13 are nano- and/orpicocells in which only terminals of the employees of said company canoperate. All three radio access networks may have cells of differentsizes offering different types of services. Additionally, cells of allthree radio access networks 12, 13 and 14 may overlap either entirely orin part. The bit rate used at a given moment of time depends, amongother things, on the radio path conditions, characteristics of theservices used, regional overall capacity of the cellular system and thecapacity needs of other users. The new types of radio access networksmentioned above are called generic radio access networks (GRAN). Such anetwork can co-operate with different types of fixed core networks CNand especially with the GPRS network of the GSM system. The genericradio access network (GRAN) can be defined as a set of base stations(BS) and radio network controllers (RNC) that are capable ofcommunicating with each other using signaling messages.

[0007]FIG. 1b shows an architecture of a general packet radio service(GPRS). The GPRS is a new service that is currently based on the GSMsystem but it is supposed to be generic in the future. GPRS is one ofthe objects of the standardisation work of the GSM phase 2+ and UMTS atthe ETSI (European Telecommunications Standards Institute). The GPRSoperational environment comprises one or more subnetwork service areas,which are interconnected by a GPRS backbone network. A subnetworkcomprises a number of packet data service nodes (SN), which in thisapplication will be referred to as serving GPRS support nodes (SGSN)153, each of which is connected to the mobile telecommunications system(typically to a base station through an interworking unit) in such a waythat it can provide a packet service for mobile data terminals 151 viaseveral base stations 152, i.e. cells. The intermediate mobilecommunication network provides packet-switched data transmission betweena support node and mobile data terminals 151. Different subnetworks arein turn connected to an external data network, e.g. to a Public DataNetwork (PDN) 155, via GPRS gateway support nodes GGSN 154. The GPRSservice thus allows the provision of packet data transmission betweenmobile data terminals and external data networks when the appropriateparts of a mobile telecommunications system function as an accessnetwork.

[0008] In order to access the GPRS services, a mobile station shallfirst make its presence known to the network by performing a GPRSattachment. This operation establishes a logical link between the mobilestation and the SGSN, and makes the mobile station available for SMS(Short Message Services) 158, 159, over GPRS, paging via SGSN, andnotification of incoming GPRS data. More particularly, when the mobilestation attaches to the GPRS network, i.e. in a GPRS attachmentprocedure, the SGSN creates a mobility management context (MM context).Also the authentication of the user is carried out by the SGSN in theGPRS attachment procedure. In order to send and receive GPRS data, theMS shall activate the packet data address wanted to be used, byrequesting a PDP activation procedure (Packet Data Protocol). Thisoperation makes the mobile station known in the corresponding GGSN, andinterworking with external data networks can commence. Moreparticularly, a PDP context is created in the mobile station and theGGSN and the SGSN. The packet data protocol context defines differentdata transmission parameters, such as the PDP type (e.g. X.25 or IP),the PDP address (e.g. X.121 address), the quality of service (QoS) andthe NSAPI (Network Service Access Point Identifier). The MS activatesthe PDP context with a specific message, Activate PDP Context Request,in which it gives information on the TLLI, the PDP type, the PDPaddress, the required QoS and the NSAPI, and optionally the access pointname (APN).

[0009]FIG. 1 also shows the following GSM functional blocks: MobileSwitching Center (MSC)/Visitor Location Register (VLR) 160, HomeLocation Register (HLR) 157 and Equipment Identity Register (EIR) 161.The GPRS system is usually also connected to other Public Land MobileNetworks (PLMN) 156.

[0010] Functions applying digital data transmission protocols areusually described as a stack according to the OSI (Open SystemsInterface) model, where the tasks of the various layers of the stack, aswell as data transmission between the layers, are exactly defined. Inthe GSM system phase 2+, which in this patent application is observed asan example of a digital wireless data transmission system, there arefive operational layers defined.

[0011] Relations between the protocol layers are illustrated in FIG. 2.The lowest protocol layer between the mobile station MS and the basestation subsystem is the layer 1 (L1) 200, 201, which corresponds to aphysical radio connection. Above it, there is located an entitycorresponding to the layers 2 and 3 of a regular OSI model, wherein thelowest layer is a radio link control/media access control (RLC/MAC)layer 202, 203; on top of it a logical link control (LLC) layer 204,205; and topmost a radio resource control (RRC) layer 206, 207. Betweenthe base station subsystem UTRA BSS of the generic radio access networkand an interworking unit/core network IWU/CN located in the corenetwork, there is assumed to be applied a so-called Iu interface, wherethe layers corresponding to the above described layers from L1 to LLCare the layers L1 and L2 of the OSI model (blocks 208 and 209 in thedrawing), and the layer corresponding to the above described RRC layeris the layer L3 of the OSI model (blocks 210 and 211 in the drawing).

[0012] The mobile station MS must include a higher-level controlprotocol 212 and a protocol 213 for serving higher-level applications,of which the former communicates with the RRC layer 206 in order torealise control functions connected to data transmission connections,and the latter communicates directly with the LLC layer 204 in order totransmit such data that directly serves the user (for instance digitallyencoded speech). In a mobile station of the GSIVI system, the blocks 212and 213 are included in the above mentioned NIM layer.

[0013] In GPRS, a Temporary Block Flow (TBF) is created for transferringdata packets on a packet data channel. The TBF is a physical connectionused by the two Radio Resource (RR) peer entities to support theunidirectional transfer of Logical Link Control (LLC) Packet Data Units(PDU) on packet data physical channels. The TBF is normally alwaysreleased when there is no data to be transmitted. This is a problem invoice services because there are silent periods in between activeperiods.

[0014] During these silent or “passive” periods no data is transferredand the TBF is thus released. The TBF setup procedure is likely to betoo long in order to be set up fast enough when the active periodcontinues.

[0015] An example of the resource allocation in the GPRS of the currentGSM Phase 2+ specification is next described in more detail.

[0016] In the GSM Phase 2+ the uplink resource allocation is currentlyspecified as follows. The Mobile Station (MS) requests uplink radioresources by sending a PACKET CHANNEL REQUEST message to the network.Various access type values are specified for the request message. Fordata transfer ‘one phase access’, ‘two phase access’ and ‘short access’access type values are defined. Using ‘short access’ access type value,the MS may request the radio resources to transfer only few RLC datablocks, and therefore it is not applicable for transferring continuousdata flows.

[0017] When a network receives a PACKET CHANNEL REQUEST messageindicating one phase access, it may allocate radio resources on one orseveral Packet Data CHannels (PDCH). The allocation is based oninformation included in the request message. The following table showsan example for an 11 bit message content of a PACKET CHANNEL REQUESTmessage: bits Packet Channel 11 10 9 8 7 6 5 4 3 2 1 Access 0 m m m m mp p r r r One Phase Access Request 1 0 0 n n n p p r r r Short AccessRequest 1 1 0 0 0 0 p p r r r Two Phase Access Request 1 1 0 0 0 1 r r rr r Page Response 1 1 0 0 1 0 r r r r r Cell Update 1 1 0 0 1 1 r r r rr Mobility Management procedure 1 1 0 1 0 0 r r r r r Measurement ReportAll others Reserved

[0018] An 11 bit PACKET CHANNEL REQUEST message indicating one phaseaccess has a field of 5 bits describing the multislot class of themobile station, a field of two bits indicating requested priority and afield of three bits describing random reference (random mobile stationidentification information).

[0019] The following table shows an example for an 8 bit message contentof a PACKET CHANNEL REQUEST message: bits 8 7 6 5 4 3 2 1 Packet ChannelAccess 1 m m m m m r r One Phase Access Request 0 0 n n n r r r ShortAccess Request 0 1 0 0 0 r r r Two Phase Access Request 0 1 0 0 1 r r rPage Response 0 1 0 1 0 r r r Cell Update 0 1 0 1 1 r r r MobilityManagement procedure 0 1 1 0 0 r r r Measurement Report All othersReserved

[0020] An 8 bit Packet Channel Request message indicating one phaseaccess has a field of 5 bits describing the multislot class of themobile station and a field of two bits describing random reference. Theinformation about the allocated radio resources is sent to the MobileStation with a PACKET UPLINK ASSIGNMENT message.

[0021] When a network receives a PACKET CHANNEL REQUEST messageindicating two phase access, it may allocate limited radio resources onone packet data channel. The allocated radio resources are transmittedto the mobile station with a PACKET UPLINK ASSIGNMENT message. Afterthis the mobile station transmits a PACKET RESOURCE REQUEST message tothe network by using the allocated radio resources. The message definesmore accurately the required radio resources, e.g. requested bandwidthand priority, and the radio capability of the mobile station. Based onthe information received in the PACKET RESOURCE REQUEST message, thenetwork may assign one or several packet data channels to the TBF andinforms the assigned radio resources to the mobile station with a PACKETUPLINK ASSIGNMENT message.

[0022] Above, the request of resources was made using the GPRS controlchannel as an example. There are also other ways of requesting resourcesin case the cell does not include a GPRS control channel (even if itsupprorts GPRS). In this case the resource request can be made using aGSM control channel.

[0023] In the prior art uplink radio resource allocation the followingproblems may arise:

[0024] If the priority field included into the PACKET CHANNEL REQUESTand the PACKET RESOURCE REQUEST Request messages does not unambiguouslydefine delay sensitive real time traffic, the network might not be ableto provide the needed radio resources for the MS. Thus, e.g.transferring speech using the GPRS might not reach a sufficient quality.

[0025] The default RLC mode is an acknowledged mode in one phase access.Since real time traffic would be transferred using unacknowledged RLCmode, two phase access should be used. Using two phase access,additional radio resource request information may be given to thenetwork. However, two phase access causes additional delay to channelassignment procedure, because the mobile station has to send two requestmessages to the network instead of one. In spite of the additional radioresource request information it is not guaranteed that the network isable to provide the needed radio resources for the mobile stationtransferring delay sensitive real time traffic.

[0026] When allocating radio resources for uplink transfer, downlinkradio resources cannot be allocated simultaneously, because the downlinktemporary block flow cannot be created without downlink packets. Thus itis possible that, when the mobile station then would receive a downlinkpacket, the network is unable to assign radio resources for the transferof the packet.

[0027] Downlink radio resource allocation is currently specified asfollows: When the network receives data for a mobile station which hasno assigned radio resources and whose cell location is known, thenetwork assigns radio resources on one or several packet data channelsby transmitting a PACKET DOWNLINK ASSIGNMENT message to the mobilestation. When the mobile station receives the assignment message, itstarts listening allocated packet data channels for Radio Link Control(RLC) data blocks.

[0028] In downlink radio resource allocation, the following problems mayarise:

[0029] If information attached to data (coming from the SGSN) does notunambiguously define delay sensitive real time traffic, the network maynot be able to provide the needed downlink radio resources for the MS.

[0030] Also if there is need to transfer delay sensitive real timetraffic to both directions, downlink and uplink, the mobile station mayrequest uplink radio resources only when the network assigns sendingpermission to the mobile station. This may cause a delay of variableamount of time, such as several seconds.

[0031] When allocating radio resources for downlink transfer, uplinkradio resources cannot be allocated simultaneously because the uplinktemporary block flow cannot be created without uplink packets. Thus itis possible, that the mobile station requests uplink radio resources butthe network is unable to assign the requested radio resources.

[0032] Uplink radio resource deallocation is currently specified asfollows: Every uplink RLC data block includes a countdown value (CV)field. It is specified in [1] that the CV shall be 15 when the mobilestation has more than BS_CV_MAX (broadcast parameter) RLC data blocksleft to be transmitted to the network. Otherwise the mobile stationindicates to the network the number of remaining RLC data blocks withthe CV field. The last RLC data block shall be sent to the network withthe CV value set to ‘0’. Specification [1] defines also that once themobile station has sent a CV value other than ‘15’, it shall not enqueueany new RLC data blocks meaning that the new RLC data blocks shall notbe sent during the ongoing TBF. Once the network receives RLC data blockwith the CV field set to ‘0’, the TBF release procedures are initiated.

[0033] In uplink radio resource deallocation, the following problems mayarise:

[0034] If delay sensitive real time data is transferred over radiointerface according to current GPRS rules, the mobile station will haveto establish several TBFs per session, because during the passiveperiods the mobile station has no RLC data blocks to send to the networkand thus the CV value ‘0’ terminates the uplink TBF. Because the TBFsetup procedure takes time, delay sensitive traffic cannot betransmitted with good quality. Also, there are no guarantees that freeradio resources are always available when the mobile station requestsuplink radio resources.

[0035] Downlink radio resource deallocation is currently specified asfollows: Every downlink RLC data block includes a Final Block Indicator(FBI) field in the RLC header. The specification [1] defines that thenetwork indicates to the mobile station the release of the downlink TBFby setting the FBI field to ‘1’. The network sets the FBI field to ‘1’when it has no more RLC data blocks to send to the mobile station. Afterreceiving RLC data block with FBI field set to ‘1’ the mobile stationshall acknowledge to the network that it has received the FBIinformation. When the network receives the acknowledgement message, theTBF is released.

[0036] In downlink radio resource deallocation, the following problemsmay arise:

[0037] If delay sensitive real time traffic is transferred over radiointerface according to current GPRS rules, the network would have toestablish several TBFs per session, because during the passive periodsthe network has no RLC data blocks to send to the mobile station andthus the FBI value ‘1’ terminates the downlink TBF. Also, there are noguarantees that free radio resources are always available when thenetwork tries to allocate downlink radio resources.

[0038] Problems also occur in assigning uplink and downlink sendingpermissions:

[0039] If delay sensitive real time data traffic is transferred onpacket data channel/channels (PDCH), it is not guaranteed that adequatesending permissions are given in order to transfer the data, because thecurrent network may not have unambiguous knowledge about delay sensitivedata being transferred.

[0040] A further problem with the prior art specification is related tothe feature that the network assigns transmission permissions for uplinkand downlink directions independently, i.e. controls which mobilestation receives data next and which mobile station may send data next.However, delay sensitive data, such as speech, has strict delayrequirements. Consequently, whenever a delay sensitive data user hassomething to transmit, it must be able to do so in order to maintain anacceptable service level. If more than one users are allocated to thesame packet data channel it is probable that at some point two or moreusers need to transmit simultaneously, and just one can be served on thechannel. In speech conversations a large proportion of the connectiontime is silence. Thus it would be possible to statistically multiplexmore than one speech user for one packet data channel. The GPRS channelreservation system, however, is not elaborate enough to support thisneed. Therefore only one user of delay sensitive data transfer can beallocated for one packet data channel, which means that the use of thechannel capacity is not optimised.

[0041] When the network notices that a mobile station wants to senddelay sensitive data in the uplink direction the network reserves asmuch uplink resources to the mobile station as is requested. Thisnaturally requires that the network has the required resourcesavailable. This may mean that the packet data channel is dedicatedtemporarily for a single mobile station in the uplink direction. Duringpassive periods in uplink delay sensitive data transfer the network mayassign uplink sending permissions of the allocated channels for othermobile stations. Since the mobile station transferring delay sensitivedata reserves the uplink capacity of the packet data channel, othermobile stations that are allocated to the same packet data channel cannot be assigned a sending permission to find out, whether they have datato send in the uplink direction. Also, if more than one mobile stationallocated to the same packet data channel would need to send delaysensitive data at the same time, only one could be served. Therefore thenetwork is forced to restrict the number of mobile stations transferringdelay sensitive data according to the number of packet data channels inorder to provide acceptable service quality.

[0042] It is thus an object of this invention to provide a method and anarrangement that offers solutions to the prior art problems. Especially,it is an object of this invention to provide a solution, in which thephysical connection of a packet radio service is kept reserved alsoduring the passive periods of a session yet the same physical resourcecan still be shared between multiple users.

[0043] The objects of the invention are fulfilled by providing aprocedure, in which a TBF may be kept functional also when there is apassive transfer period between the mobile station and the network. Theprocedure supports delay sensitive traffic while utilizing radioresources efficiently.

[0044] One idea of the invention is that the network is informed at theend of an active period, on whether a passive period follows the activeperiod or if the connection can be released. The network may also beinformed on whether the packet data channel can be assigned to othertemporary block flows. The information can be transferred e.g. on thepacket data channel during an active period or on a control channel atany time. On the packet data channel the information can be transferrede.g. in the MAC header field of a data block. Alternatively a separatesignalling message can be used. With this information it is possible tokeep the created temporary block flow available even when there is nodata to be transmitted. When an active period starts after a passiveperiod, the connection starts using the created TBF again, and possibleother users of the packet data channel may be assigned to otherchannels.

[0045] In addition to transferring information between the mobilestation and the network on whether a passive period follows the activeperiod or if the connection can be released, there is also analternative method: The network may use a timer function for determiningwhether a passive period follows the active period or if the connectioncan be released. In this alternative, when a predetermined time ofinactive data transfer has passed, the TBF is released.

[0046] An object of the invention is also fulfilled with the idea ofallocating several delay sensitive data flows to the same packet datachannel. On an uplink channel, after one mobile station starts totransmit, the other mobile stations may be reallocated to other channelsimmediately or a transmission permit can be periodically allocated tothe mobile stations so that the mobile stations may indicate theirwillingness to transfer. On a downlink channel, after one mobile stationstarts to transmit, the other mobile stations may be reallocated toother channels immmediately as well or the data may be transferred notuntil another mobile station starts to receive data on the same channel.

[0047] An object of the invention is further fulfilled with the idea ofinforming the network on a need to allocate a TBF also in the oppositedata transfer direction. For example, when uplink TBF is allocated, alsothe downlink TBF is allocated even if no downlink data is to betransferred at the moment. This information can be transferred in asignalling message as a separate information element or in aninformation element of another purpose. The temporary data flows canalso be allocated automatically in both data transfer directions (e.g.during a connection establishment phase), when the data is delaysensitive.

[0048] An object of the invention is further fulfilled with the idea ofinforming the network on whether the data to be transferred is delaysensitive. This information can be given to the network for example in apriority field included in a Quality of Service profile informationelement.

[0049] The present invention offers important advantages over prior artmethods. With the present invention it is possible to use the packetchannel resources very effeciently. Still, if the total capacity of thenetwork is sufficient, it is possible to avoid the risk that there is nochannel available when the passive data transfer period ends.

[0050] It is characteristic to a method according to the presentinvention for transferring a data flow by creating a connection on apacket radio service of a telecommunication system, wherein the dataflow comprises at least one active data transfer period, thatinformation is transferred between the mobile station and the network onwhether after the active data transfer period a passive period starts orwhether a connection release is allowed.

[0051] The invention also applies to a telecommunications system fortransferring a data flow by creating a connection on a packet radioservice, wherein the data flow comprises at least one active datatransfer period, having the characteristic means for receivinginformation on whether after the active data transfer period a passiveperiod starts or whether a connection release is allowed.

[0052] The invention also applies to a mobile station for transferring adata flow by creating a connection on a packet radio service to acellular telecommunications system, wherein the data flow comprises atleast one active data transfer period, comprising means for transferringinformation on whether after the active data transfer period a passiveperiod starts or whether the connection release is allowed.

[0053] Preferred embodiments of the invention are been presented independent claims.

[0054] In the following the invention is described in more detail bymeans of the attached drawings in which

[0055]FIG. 1 illustrates a prior art cellular communications system,

[0056]FIG. 2 illustrates protocol levels of a prior art cellularcommunications system,

[0057]FIG. 3 illustrates a prior art MAC header in an uplink RLC datablock,

[0058]FIG. 4a illustrates a MAC header in an uplink RLC data blockwithout a TBF release indication,

[0059]FIG. 4b illustrates a MAC header in an uplink RLC data block witha TBF release indication,

[0060]FIG. 5 illustrates a flow diagram for the transmission of theuplink RLC blocks,

[0061]FIG. 6 illustrates a flow diagram for the reception of the uplinkRLC blocks,

[0062]FIG. 7 illustrates a flow diagram for the transmission of thedownlink RLC blocks,

[0063]FIG. 8 illustrates a flow diagram for the reception of thedownlink RLC blocks,

[0064]FIG. 9 illustrates TDMA frames of active and passive periods of adelay sensitive data flow and

[0065]FIG. 10 illustrates a block diagram of a mobile station accordingto the invention.

[0066]FIGS. 1 and 2 were described above in the prior art description.In the following, first principles of indicating a delay sensitive dataand of allocating resources is described using an embodiment in a GPRSsystem as an example. Next an example of placing the release informationinto the MAC header is described referring to FIGS. 3, 4a and 4 b. Nextthe phases of the inventive method are described referring to FIGS. 5-9.Finally a mobile station and a cellular system according to theinvention are shortly described referring to FIG. 10.

[0067] In an uplink resource allocation, a mobile station indicates tothe network that it requires radio resources for delay sensitive datatransfer. The network needs the information in order to assignsufficient radio resources for the mobile station to provide therequired service level. The information may be provided to the networkvia one of the following ways, where some system-specific messagedenominations are used as examples with no intention to limit theapplicability of the invention:

[0068] The mobile station sends a PACKET CHANNEL REQUEST message to thenetwork, and the message has a specific type for delay sensitive datatransfer;

[0069] CHANNEL REQUEST DESCRIPTION information element or othercorresponding information element is included into a PACKET RESOURCEREQUEST message and the information element includes informationindicating that delay sensitive data is to be transferred or;

[0070] A priority field or other field is included in the radio resourcerequest message, such as a PACKET CHANNEL REQUEST or a PACKET RESOURCEREQUEST message, that is transmitted by the mobile station to thenetwork and the field identifies unambiguously that delay sensitive datais to be transferred.

[0071] In addition to the information on that radio resources that arerequired for the delay sensitive data transfer, the radio requestinformation may also include the following additional parameters thatspecify more accurately the required resources;

[0072] The number of required packet data channels;

[0073] The information on whether the communication is unidirectional orbidirectional.

[0074] This makes the network able to determine whether the mobilestation requires also downlink resources. By reserving downlinkresources simultaneously with the uplink radio resources it is possibleto avoid a situation where the mobile station would receive downlinkdata but the network is unable to reserve downlink radio resources atthat moment;

[0075] The information on the number (N) of passive block periods. Ifthe mobile station has no data to be transmitted to the network, thenetwork may give the next N uplink sending permissions to some othermobile station/mobile stations. The mobile station or the network maydefine the value of this parameter or it may have a default value.

[0076] As the length of the PACKET CHANNEL REQUEST message is only 11 or8 bits, it may be difficult to include the above parameters into themessage. Therefore it may be preferable to use two phase access whenrequesting radio resources for delay sensitive data transfer, if a moreaccurate description of the requested radio resources is necessary.

[0077] There may also be default values for the channel request when onephase access is used. For example, when requesting radio resources fordelay sensitive data transfer one packet data channel and only uplinkradio resources could be reserved as a default. If there is a need toreserve several packet data channels the modification of the radioresources can then take place through an additional signallingprocedure.

[0078] In a downlink resource allocation, the procedure starts when thenetwork needs to transmit data to the mobile station that has nodownlink radio resources assigned or when the mobile station requeststhe establishment of a downlink TBF during an uplink TBF establishmentprocedure. The network allocates sufficient radio resources based on theinformation that is attached to the packet data. The informationincludes an indication that radio resources are required for delaysensitive data transfer so that the network can assign sufficient radioresources in order to provide the required service level. For example,the delay sensitivity of the data may be indicated in a informationelement included into the quality of service (QoS) profile. Delaysensitivity of the data transfer may also be indicated in a new field inthe QoS profile or in a new information element that is attached to thedata sent from the network, eg. from a SGSN, to the BSS.

[0079] In addition the following parameters may be included into theinformation that is received from the SGSN in order to describe therequired radio resources more accurately:

[0080] The number of required packet data channels;

[0081] The information on whether the communication is unidirectional orbidirectional. This makes the network able to determine whether themobile station requires also uplink radio resources. By reservingdownlink resources simultaneously with the uplink radio resources it ispossible to avoid a situation where the mobile station would need tosend uplink data but the network is unable to reserve uplink radioresources at that moment;

[0082] The information on the number (N) of passive block periods. Ifthe mobile station has no data to be transmitted to the network, thenetwork may give the next N uplink sending permissions to some othermobile station/mobile stations. The mobile station or the network maydefine the value of this parameter or it may have a default value.

[0083]FIG. 3 describes a prior art MAC header in uplink RLC data blockcurrently specifed in [1]. In the header the Payload Type fieldindicates the type of data contained in remainder of the RLC/MAC block.The Countdown Value field CV is sent by the mobile station to allow thenetwork to calculate the number of RLC data blocks remaining for thecurrent uplink TBF. This was already discussed above.

[0084] The Stall Indicator (SI) bit indicates whether the RLC transmitwindow of the mobile station can advance, i.e. the RLC transmit windowis not stalled, or whether it can not advance, i.e. the RLC transmitwindow is stalled. The mobile station sets the SI bit in all uplink RLCdata blocks. In RLC unacknowledged mode SI shall always be set to ‘0’.

[0085] The Retry (R) bit indicates whether the mobile stationtransmitted the PACKET CHANNEL REQUEST message once or more than onetime during its most recent channel access.

[0086] When delay sensitive data is transmitted from the mobile stationto the network according to the invention, the RLC/MAC data block mayinclude a field indicating if the RLC block is the last one of theconnection or if it is not. This field is called TBF Release (TR) inthis text. If the RLC block is the last one, the TR field is set tovalue “1”, and the TBF is concidered to be released. Otherwise the theTR field is set to “0” and the network then consideres the TBF to beopen. The TR field may e.g. replace the stall indicator SI field,because when the RLC operates in unacknowledged mode the SI field is notused. The TR field may also be included in the CV field by replacing apart of it.

[0087] When delay sensitive data is transmitted to the network, theRLC/MAC data block includes information on whether the mobile stationhas more RLC data blocks to be transmitted or if the network may givenext N uplink transmit permissions to other mobile stations. Thisinformation may also be provided to the network in the RLC/MAC headerand the field is called “CV′” in this text. The CV′ field may replaceall or part of the CV field in the prior art specification.

[0088] When the mobile station transfers delay sensitive data to thenetwork and the CV′≠0 the network interprets it so that the mobilestation has more data blocks to be transmitted and the network is thusable to assign also the next uplink transmit permissions for the samemobile station. When the CV′ value is set to “0” the network interpretsit so that the first mobile station has no more RLC data blocks to betransmitted at the time and the network may therefore give the next Nuplink transmit permissions to some other mobile station/stations.However, in order to guarantee that the first mobile stationtransferring delay sensitive data does not need to wait too long for anuplink transmit permission the network gives at every N block period anuplink transmit period for the first mobile station. If the mobilestation then has RLC data blocks to be transmitted, the mobile stationincludes TR and CV′ fields in the RLC data blocks as described above. Ifthe mobile station does not have data to be transmitted, to the networkat the time, the mobile station may omit the uplink transmit permissionor it may transmit a Packet Dummy Control Block or a signalling message.

[0089] If the downlink temporary block flow is preserved also when thereis no data to be transmitted to the mobile station and if the network isunable to determine when to release the downlink TBF, the mobile stationshould tell the network when the downlink TBF can be released. This canbe accomplished by introducing a bit in the RLC/MAC data block headerthat indicates whether the network is to release both uplink anddownlink temporary block flows. The mobile station may also transmit aRLC/MAC control signalling message to the network indicating the releaseof downlink temporary block flow prior to the release of the uplinktemporary block flow. It is also possible to have a timer function whichwould release the downlink temporary block flow after a predeterminedtime has passed from the latest transmission of downlink data. Thenetwork may contain a logical entity that is able to determine, when theTBF is to be released

[0090]FIG. 4a describes an example of the MAC header in uplink RLC datablock according to the invention, without including a downlink TBFrelease indication. The TBF Release (TR) indicates whether the mobilestation transferring delay sensitive data requests the release of uplinkTBF or not.

[0091]FIG. 4b describes an example of the MAC header in uplink RLC datablock according to the invention, including Downlink TBF Releaseindication DTR in the bit 6 of the header. The downlink TBF releaseindicates whether the mobile station transferring delay sensitive datarequests also the release of downlink TBF or not. The DTR field, ifused, may be present in all uplink RLC data blocks thus occupying e.g.one Count Value CV′ field bit. DTR field may actually be included intoMAC header only when CV′ field is set to ‘0’ (actually three LSBs) andTR field is set to ‘1’, thus leaving 4 bits for CV′ field in normaloperation.

[0092] The parameters according to the invention can be included intothe current uplink RLC/MAC data block as described above, or a newRLC/MAC data block may be defined. If a new data block would be defined,the Payload Type may be used for identifying the type of the block.

[0093]FIG. 5 shows a flow diagram of the steps for transmitting a RLCblock from a mobile station to the network, 500. The followingparameters of a MAC header field are given as examples; many other waysof transferring the information can be applied. In step 502, the mobilestation checks whether the RLC block to be transmitted is the last onein a data block of the TBF. If it is, the mobile station sets theparameters CV′=0 and TR=1 of the MAC header, step 504, and transmits theblock. The parameter TR=1 means that the TBF can be released, step 506.

[0094] If in step 502 the RLC block is not the last one of the TBF, themobile station checks in step 510, whether the RLC block is the last onein the buffer. If it is, the mobile station sets the parameters CV′=0and TR=0 in step 512 and transmits the block. This means that the dataflow starts a passive period, but the TBF is not released. If the RLCblock is not the last one in the buffer of the mobile station, theparameters are set CV′=other than 0 and TR=0 in step 520, and the blockis transmitted. The CV′ value can be the number of the remaining blocksin the buffer, if the number is small enough to be expressed in CV′. Forexample, the CV′ can be used as the CV parameter in the currentspecification (ETSI GSM 06.60).

[0095] After the block is transmitted in any of the previous steps, theoperation is continued from step 500, when there is a data block in thebuffer to be transmitted, 530.

[0096]FIG. 6 shows a flow diagram of the steps for receiving a RLC blockfrom a mobile station to the network, 600. In step 602 the networkchecks the value of the TR parameter from the received RLC block. If theparameter TR=1, the uplink TBF is released, step 604. Next, the releaseof the downlink TBF depends on whether it is requested, steps 606 and608.

[0097] If in step 602 the parameter TR=0, the network next checks thevalue of the parameter CV′, step 610. If CV′=0, this means that there isa passive transfer period in the data flow, and the packet data channelmay be scheduled for another mobile station (other mobile stations),step 612. If, however, the parameter CV′ is different from 0, thechannel permission is scheduled for the same mobile station, step 620.

[0098] After the block is received and processed in the previous steps,630, the operation is continued from step 600, when there is a new datablock received.

[0099]FIG. 7 shows a flow diagram for the transmission of the RLC blocksfrom the network to the mobile station, 700. In step 702, the networkchecks whether the RLC block to be transmitted is the last one in a datablock of the TBF. If it is, the mobile station sets the parameter FinalBlock Indicator FBI=1. It also sets a valid Relative Reserve BlockPeriod (RRBP) field, step 710, and transmits the block, step 720. Theparameter FBI=1 means that the current block is the last RLC block inthe temporary block field and thus the TBF can be released. Theallocation of a RRBP field means that one uplink transmit block isallocated for the receiving mobile station so that the mobile stationcan send a control message to the network.

[0100] If in step 702 the RLC block is not the last one of the TBF, thenetwork sets the parameter FBI=0 in step 704. This means that the dataflow may or may not start a passive period, but the TBF is not released.The network also sets a valid RRBP if needed, step 704.

[0101] After this, the network transmits the data block, step 720. Afterthe block is transmitted in any of the previous steps, the operation iscontinued from step 700, when there is a data block in the buffer to betransmitted, 730.

[0102]FIG. 8 shows a flow diagram of the steps for receiving a RLC blockfrom the network to a mobile station, 600. In step 602 the mobilestation checks the value of the FBI parameter from the received RLCblock. If the parameter FBI=1, the downlink TBF release procedure isinitiated, step 810. If in step 802 the parameter FBI≠1, this means thatthe mobile station continues the receive procedure of the present TBF,step 830.

[0103]FIG. 9 shows successive TDMA frames, in which time slot 5 is usedfor a packet data channel. In the TDMA frames 900 and 902, the packetdata channel is allocated for an active connection of delay sensitivedata transfer. As the active period changes into a passive (silent)period, the network assigns a transmit permission to a second connectionin frame 904. During the passive period, frames 904-912, the networkalso periodically assigns sending permissions to the mobile station ofthe first connection for a channel request, frame 908. As the activeperiod starts again, frames 914, 916, the permission for an uplink datatransfer may be given back to the first connection. If the secondconnection is transferring delay sensitive data as well, then one of theconnections may be reallocated to another packet data channel at thebeginning or at the end of the passive period.

[0104] When the same packet data channel is allocated for severalpassive connections all the other delay sensitive users can bereallocated to other packet data channels when one of them startstransmitting. Alternatively they may wait for an uplink transmissionpermit on the same packet data channel. In practice the reallocation maybe carried out by sending a signalling message, such as a PACKET UPLINKASSIGNMENT, containing new packet data channel allocation to each mobilestation being reallocated. Another alternative is to send a singlesignalling message, such as a PACKET REALLOCATION, containing new packetdata channel allocations to all/some mobile stations being reallocated.Using only one signalling message leaves more free radio capacity forother purposes.

[0105] When the network receives delay sensitive data for a mobilestation, the network reserves as much downlink packet data channelcapacity to the mobile station as is needed. This naturally requiresthat the network has the needed resources available. This may mean thatthe packet data channel is dedicated temporarily for a single mobilestation in the downlink direction. During the passive periods indownlink delay sensitive data transfer the network may assign downlinktransmission permissions to other mobile stations and thus the networkcan transmit data to other mobile stations. In order to prevent asituation where the network receives delay sensitive data to more thanone mobile station simultaneously on the same packet channel/channelsand thus would have to block all but one, the network may distribute theother mobile stations using delay sensitive data transfer to otherpacket data channels. The distribution can be made using the followingmechanisms:

[0106] Early downlink assignment: When the network receives delaysensitive data for a mobile station, it reallocates the other delaysensitive data users residing on the same packet data channel. Delayinsensitive data users may be reallocated to other packet data channelsor alternatively they will wait for a transmission permit on the samepacket data channel. The network transmits a signalling message, such asa PACKET DOWNLINK ASSIGNMENT, containing new packet data channelallocations to all/some mobile stations being reallocated.

[0107] Late downlink assignment: When the network receives delaysensitive data for a mobile station, it does not immediately reallocatethe other mobile stations residing on the same packet data channel. Onlywhen the network receives delay sensitive data for a mobile station andthe network is already transferring delay sensitive data to some othermobile station on the same packet data channel, the network assigns anew packet data channel to the mobile station. The new packet datachannel is assigned, e.g. by sending a PACKET DOWNLINK ASSIGNMENTsignalling message to the mobile station.

[0108] The network should control that the delay sensitive data does notneed to queue too long for a downlink transmission permit. The networkshould also control that the signalling messages related to the othertemporary block flows of other mobile stations do not excessively occupythe packet data channel. This may be accomplished by giving the same ora higher priority to the delay sensitive data transfer compared tosignalling messages of other temporary block flows.

[0109] When the network has temporarily no delay sensitive data to betransmitted, it preserves the temporary block flow and does not set theFBI field to value “1” after transmitting the the last buffered RLC datablock. The mobile station controls the termination of the downlink TBFor the network may contain a logical entity that is able to determine,when the TBF is to be released.

[0110]FIG. 10 shows a block diagram of a mobile station 100 according tothe invention. The mobile station comprises an antenna 101 for receivingradio frequency signals from base stations. The received RF signal isled with the switch 102 to the RF receiver 111, in which the RF signalis amplified and converted digital. Thereafter the signal is detectedand demodulated in block 112. The type of the demodulator depends on thesystem radio interface. It may include a QAM demodulator, or a RAKEcombiner. The deciphering and deinterleaving is made in block 113. Afterthis, the signal is processed according to the signal type(speech/data). The received packet data can be converted acoustic with aloudspeaker, or the received packet data can be linked to a separatedevice, such as a video monitor. A control unit 103 controls thereceiver blocks according to a program that is stored into a memory 104.

[0111] In the transmission of a signal, the control unit controls thesignal processing block 133 according to the type of signal. Block 121further makes the ciphering and interleaving for the signal. Bursts areformed from the coded data in block 122. The bursts are furthermodulated and amplified in block 123. The RF signal is led to theantenna 101 via the switch 102 for transmission. The processing andtransmission blocks are also controlled by the control unit. Especiallythe control unit controls the transmission blocks in such a way that theMAC header parameters of the RLC block are coded and transmittedaccording to the present invention. Also the channel selection iscontrolled by the control unit in such a way that the assigned packetdata channel is used according to the invention.

[0112] In general, the processing of information in a telecommunicationdevice takes place in an arrangement of processing capacity in the formof microprocessor(s) and memory in the form of memory circuits. Sucharrangements are known as such from the technology of mobile stationsand fixed network elements. To convert a known telecommunication deviceinto a telecommunication device according to the invention it isnecessary to store into the memory means a set of machine-readableinstructions that instruct the microprocessor(s) to perform theoperations described above. Composing and storing into memory of suchinstructions involves known technology which, when combined with theteachings of this patent application, is within the capabilities of aperson skilled in the art. On the network side, the features accordingto the invention can be implemented e.g. in the Packet Control Unit PCUthat assigns e.g. uplink and downlink sending permissions for mobilestations. The packet control unit may be located e.g. in the BaseTranceiver Station BTS, Base Station Controller BCS or Serving GPRSSupport Node SGSN.

[0113] Above, an examplary embodiment of the solution according to theinvention has been described. The principle according to the inventioncan naturally be modified within the frame of the scope defined by theclaims, for example, by modification of the details of theimplementation and ranges of use.

[0114] The information on the following data transfer period can betransferred on the packet data channel, or it may as well be transferredin a signalling message on some control channel such as SACCH (SlowAssociated Control CHannel) of the GSM system. Thus also the parametersin a MAC header field of an RLC block are given as examples only; manyother signalling possibilities exist for transferring the correspondinginformation. Especially the use of the SACCH or a comparable controlchannel will enable the transmission of such information at any time,irrespective of whether there is currently an active period or not.

[0115] The invention is not in any way restricted to transferring speechdata, but it can be applied in a packet radio service where any dataflows with passive and active periods are transferred. One example isvideo data transfer, wherein a moving/changing video image would requirean active data flow and still video image periods which would notrequire data transfer for the image update.

[0116] Cited Documents:

[0117] [1] Digital cellular telecommunications system (Phase 2+);General Packet Radio Service (GPRS); Mobile Station (MS)-Base StationSystem (BSS) interface; Radio Link Control/Medium Access Control(RLC/MAC) protocol (GSM 04.60 version 6.1.0); EuropeanTelecommunications Standards Institute

1. A method for transferring a data flow by creating a connection on apacket radio service of a telecommunication system, said connectionconstituting a packet data channel, wherein the data flow comprises atleast one active data transfer period, characterised in that informationis transferred between the mobile station and the network on whetherafter the active data transfer period a passive period starts or whethera connection release is allowed.
 2. A method according to claim 1,characterized in that said information is transferred during the activedata transfer period.
 3. A method according to claim 1, characterised inthat said information is transferred on the packet data channel.
 4. Amethod according to claim 3, characterised in that the data flow isarranged to consist of data blocks, and said information is transferredin a header of a data block.
 5. A method according to claim 4,characterised in that the radio service is GPRS and the header is a MACheader of a RLC block.
 6. A method according to claim 1, characterisedin that it comprises the step of creating a control connection betweenthe mobile station and the network, said control connection beingseparate from said packet data channel and constituting a controlchannel, wherein said information is transferred on the control channel.7. A method according to any of claims 1-6, characterised in that whenthe same packet data channel is allocated for more than one connectionof delay sensitive data, all such connections having a passive period,and when a first connection changes to an active transfer period, asecond connection is reallocated to another packet data channel.
 8. Amethod according to claim 7, characterised in that said secondconnection is reallocated to another packet data channel essentiallyimmediately after said first connection has become active.
 9. A methodaccording to claim 7, characterised in that said second connection isreallocated to another packet data channel, when said second connectionbecomes active.
 10. A method according to any of the previous claims,characterised in that when a passive data transfer period follows anactive data transfer period, the network allocates a number of transmitpermissions that can be allocated to other temporary block flows on thepacket data channel.
 11. A method according to any of the previousclaims, characterised in that when allocating data transfer resourcesfor a first direction (uplink/downlink) of packet data transfer,resources are also allocated for packet data transfer of the oppositedata transfer direction.
 12. A method according to claim 11,characterised in that the resource allocation in the opposite datatransfer direction is initialised with a message between the mobilestation and the network.
 13. A method according to any of the previousclaims, characterised in that when releasing a temporary block flow in afirst direction (uplink/downlink) of packet data transfer, a temporaryblock flow in the opposite data transfer direction is maintained atleast for a predetermined time.
 14. A method according to any of claims1-12, characterised in that the release of the downlink temporary blockflow is initialised with a message between the mobile station and thenetwork.
 15. A method according to any of the previous claims,characterised in that the network is informed on whether the packet datato be transferred is delay sensitive.
 16. A telecommunications systemfor transferring a data flow by creating a connection on a packet radioservice, wherein the data flow comprises at least one active datatransfer period, characterised in that the cellular communicationssystem comprises means for receiving information on whether after theactive data transfer period a passive period starts or whether aconnection release is allowed.
 17. A telecommunications system accordingto claim 16, characterised in that the system comprises means forallocating the same packet data channel for at least two connections ofdelay sensitive data, both connections comprising a passive period, andmeans for reallocating a second connection to another packet datachannel after a first connection becomes active.
 18. A mobile stationfor transferring a data flow by creating a connection on a packet radioservice to a cellular telecommunications system, wherein the data flowcomprises at least one active data transfer period, characterised inthat the mobile station comprises means for transmitting information onwhether after the active data transfer period a passive period starts orwhether a connection release is allowed.
 19. A mobile station accordingto claim 18, characterised in that the means for transmitting theinformation comprises means for transmitting the information in the MACheader of a RLC block in GPRS.
 20. A method for transferring a data flowby creating a connection on a packet radio service of atelecommunication system, wherein the data flow comprises at least oneactive data transfer period, characterised in that after an active datatransfer period the connection is maintained for a predetermined time,whereafter the connection is released.